Category Archives: Computers

The Spare Box

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I don’t blame the OS directly, but life in Windows-land always involves me sitting around twiddling my thumbs.

So I brought back an ancient laptop with me. 512MB RAM (I think–it might be 256), a slow processor, a tiny hard drive, and a battery that doesn’t hold a charge. It’s running Ubuntu, and its two duties are as a web browsing machine and an IM machine.

So now while the system is unusable, I can get stuff done over here.

(Psst: Steam, when your game is so hard to start that I lose interest before it’s launched, you’ve failed miserably. Go get stuck in a lift. A burning lift.)

Terrible Software

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Two different things that boggled my mind today:

  • CCleaner offered clean up Symantec’s log files. All 5 gig of them. (?!?!)
  • Team Fortress 2 just crashed after spending about ten minutes “loading.” It complained that there wasn’t enough memory and that I probably had the paging file disabled. The latter is true: I never recreated it after disabling it since it was in 600 pieces. But RAM? I’ve got 2 GB of it. If you can’t write code to fit in that, you deserve to be stuck in a lift. A burning lift. With a corpse.

Seriously, 2 GB RAM isn’t enough to load the game? And you need 5 GB of log files?

Mailing Lists

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Mailing lists are dangerous things. Especially when you’re the admin of them.

I run one for a list of about 100 members in one of my clubs. The other is a list of board members for a second club, which has about 10 members. To start, I set Kyle’s Blackberry address up as a “moderator,” intending to whitelist him for sending to the list. In actuality, moderator status means that he receives an e-mail every time a member is added or removed from the list. And I proceeded to do a bulk-addition of all 100 addresses, which resulted in the server simultaneously sending him 100 electronic missives, which apparently caused the phone to “buzz like an angry hornet” before crashing.

Just now, I got the two lists confused. Fortunately, I did it the less dangerous way: sending an announcement meant for the 100 people to the 10-member board of the other club, all of which are good friends of mine who expect me to do dumb things like that. It would have been much worse had I instead sent some sort of sensitive material to a list of 100 people I hardly know, expecting to send it to the list of 10.

The Thing with the Rows?

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After years of not knowing any better, I finally learned the answer to, “Are you good with Excel?”

It’s an emphatic, “No.”

Of course I actually know my way around it really well. But, every single time, I have soon realized that I’d have been better off lying. “Hey Matt, I have this list of numbers and I want to find the standard deviation” would be easy. So wouldn’t, “How can I get this formula to apply to these cells?”

But, “Why isn’t my data importing from Excel to PowerPoint properly?” I don’t have the foggiest clue. Why doesn’t some complex formula you wrote work? I don’t know, you wrote it! Why doesn’t the SQL in your query work? Wait, what? You asked me about Excel.

I’m warning you. When someone asks you, say no, play dumb (“Naw, I don’t get it at all… That’s the thing with them numbers and rows, right?”) And, if there’s any signs that they’re not taking no for an answer, simply turn and run.

MiniAjax — An Awesome Site

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Web developers, check it out. My one complaint is that this is an awkward assortment of things ranging from little JavaScript snippets to free (GPL) apps to proprietary, expensive applications. But there are some very cool ones in there. (Psst! Heatmap is running on this site! It’s going to take a while to build up enough data worth sharing, but I’ll let you know when the time comes.) Some of the other ones are going to make their way into some projects I’m working on.

Malus Fide

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I’ve always like the idea of rewarding douchebaggery with more douchebaggery. And one bit of douchebaggery that really bugs me is that, running a webserver, it’s always getting requests for pages that have never existed. What’s going on is that people are probing for common vulnerabilities. I don’t have a /phpmyadmin, but I get multiple requests a day for it. (I do have PHPMyAdmin, but it’s up to date, secure, and at an obscure URL.) Same goes for awstats.

What I’ve always wanted to do is respond to these requests with complete garbage. Unending garbage. My long-time dream was to link a page to /dev/random, a “file” in Linux that’s just, well, random. (It’s actually a device, a software random number generator.) The problem is that linking it is full of problems, and, when you finally get it working, you’ll realize that it’s smart enough to view it as a device and not a file.

So I took the lazy route and just created a 500MB file. You use dd to copy data from a disk, with /dev/urandom as the input and a file with a .html extension as output. I had it read 500 “blocks” of 1MB. Granted, this is a total waste of disk space, but right now I have some spare space.

Of course, I was left with a few resources I was concerned about: namely, RAM, CPU time, and network activity. I use thttpd for this idiotic venture, which lets me throttle network activity. I’ve got it at 16 KB/sec right now. (Which is an effective 128 kbps.) This ensures that if it gets hit a lot it won’t put me over my (1,000 GB!) bandwidth allocation.

Apparently, though, this throttling solves the problem: at first glance, it looks like it’s smart enough to just read 16KB chunks of the file and send them out, as opposed to trying to read it into memory, which would kill me on CPU time and RAM. So the net result is relatively minimal resource utilization.

Currently, it’s just sitting there at an obscure URL. But my eventual plan is to setup a /awstats and a /phpmyadmin and a /admin and a /drupal and have them all throw a redirect to this file.

The other bonus is that, at 16KB/sec, if a human gets there, they can just hit “stop” in their browser long before a crash is imminent. But, if it works as intended, infected systems looking to spread their worms/viruses won’t be smart enough to think, “This is complete gibberish and I’ve been downloading it for 30 minutes now” and will derail their attempts at propagating.

It’s not in motion yet, though… But I’ll keep you posted.

Filesystems

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On my continuing obsession with squeezing every bit of performance out of this system… They say that Linux filesystems don’t get fragmented. I never understood this. It’s apparently smarter about where files are placed. But still, frag-proof? If it was that easy, other filesystems would have figured it out long ago too. I figured that the explanation was just over my head. In reality, the “explanation” is that it’s a myth.


oxygen bin # fragck.pl /home
2.19458018658374% non contiguous files, 1.03385162150155 average fragments.
oxygen bin # fragck.pl /var/log
56.3218390804598% non contiguous files, 28.9425287356322 average fragments.
oxygen bin # fragck.pl /var/www/
1.45061443222766% non contiguous files, 1.05527580153377 average fragments.
oxygen bin # fragck.pl /etc
2.18023255813953% non contiguous files, 1.05450581395349 average fragments.
oxygen bin # fragck.pl /var/lib/mysql/
16.5424739195231% non contiguous files, 2.93740685543964 average fragments.

The results kind of make sense: /var/log is full of files where you’re constantly appending a line or two to various files, so it only stands to reason that, if the filesystem isn’t very careful, fragmentation would build up. The other one is /var/lib/mysql, where MySQL stores its data. It’s the same deal as /var/log, really, in that it’s continually adding files.

/var/log/messages, the system log file, is in 75 pieces. Its backup, messages.1.gz,was in 68.

Realistically the performance hit is negligible. It’s not like a core system file is in hundreds of pieces. (Like, say, the paging file!) /bin has very low fragmentation. Log files can be fragmented an not impact anything. (Except my OCD.) Although I am concerned about MySQL’s data stores building up fragmentation. In theory I can bring the database down and shuffle the files around, but it’s probably best left alone right now.

Fortunately, there’s hope… By moving a file to another partition, you cause it to move physical locations. Something like mv messages /tmp/ramdisk && mv /tmp/ramdisk/messages . will cause the file to be rewritten. (Granted, this particular command was an awful idea: syslog-ng keeps /var/log/messages open, and doesn’t like it when the file randomly disappears. The fact that it was only gone for a split-second doesn’t change the fact that the files location has changed.) Although don’t get too excited about this: for some reason, fragmentation sometimes ends up worse! access_log was in 60 pieces. Now it’s in 76.

I’ve also heard it said that some fragmentation isn’t necessarily a bad thing: a few files close together on the disk with light fragmentation is better than frag-free files on opposite ends of the disk. But that doesn’t satisfy my OCD. I guess the moral of the story is to not muck around too much with things. Or, “if it ain’t broke, don’t fix it!”

M/S Explorer Crashes Again

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M/S Explorer has crashed.

For added irony, they were in penguin territory at the time.

(One wonders the view out the Windows now that the ship is on its side–they’re most likely blue screens! No Word on whether that is the case, of course, but I will say that the ship’s Outlook isn’t so good. Fortunately, because the rescuers Excel at what they do, passengers were able to Exchange their rooms for ones on a stable ship. Because there were no fatalities, this was not FrontPage news, except on Digg.)

Speeding up MySQL with tmpfs?

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I’m still getting a decent percent of files being created on disk in queries, even though my tmp_table_size is an astonishing 128MB. (The whole blogs database uses about 6MB of disk.)

The problem is described here: TEXT and BLOB queries apparently don’t like being in memory. This page explains it further.

The problem is that… These are blogs. Aside from some trivial cross-table type stuff, every single query uses TEXT queries. Interestingly, the solution everyone proposes is using a ramdisk. I was somewhat concerned about using a ramdisk, though: for one, the procedure for creating it looked somewhat arcane, and one place talking about it mentioned that his 16MB of ramdisk was almost as big as his 20MB hard drive. I think of my old 20GB hard drive as ridiculously old. The other reason, though, is that ramdisk is scary: it’s a finite size. I’d love something like a 1GB ramdisk for /tmp, but I don’t even have a gig of RAM, much less a gig to allocate for file storage.

Enter tmpfs. In a nutshell, it’s like tmpfs, but the size can be dynamic, and it can swap, which means I don’t have to worry about my 16MB tmpfs partition trying to store 17MB of data and blowing up. Creation was eerily easy:

# Make a directory to use as a mountpoint, and give it a misleading name
mkdir /tmp/ramdisk

# Mount it as type tmpfs
mount -t tmpfs tmpfs /tmp/ramdisk -o size=16M,mode=1777

In my.cnf, it’s as easy as changing tmpdir=/tmp/ to tmpdir=/tmp/ramdisk/.

And now, we let it run for a while and see how performance feels.